Fibre optic cables are presently used in such areas as voice and data transmission in the computer and communications industries. While fibre optic cables are very efficient optically for such uses, leading to low signal losses through the cables, one of the present drawbacks to their use is the complexity of the field termination, that is splicing of two free ends of fibre optic cable. It should be understood that two fibres to be connected must be very precisely aligned in an abutting manner, without the presence of such discontinuities as gaps and the like between the end faces of the two fibres. A gap between two end faces causes reflection of the incident light due to the mismatch of the index between the two compounds. That is, air is present within the gaps and rough surfaces which can cause the scattering of the light and attenuation of the signal. Thus, this is the difficulty which presents itself in the field, the preparation of optical fibres for their abutting connection without the use of precisely controllable equipment. Presently, two methods of field termination of plastic core fibre optic cables are utilized.
The first method is to provide a plastic ferrule for insertion of a free end of a fibre optic cable therethrough. The fibre optic cable is glued to the inner periphery of the ferrule and the end of the cable has to be ground down to provide a smooth abutting surface for a similar free end of a mating fibre cable. It should be appreciated that the grinding process is not an easy one to control while in the field without a controlled environment, such as a manufacturing facility where tolerances can be kept to a minimum by the use of high quality machine tools.
A second method is similar to the first method except, rather than grinding the free end of the fibre optic cable, a hot plate is provided by the end user where the hot plate is abutted the jagged edge of the free end to melt the free end of the fibre optic cable to provide a flat, smooth surface. This method is particularly difficult to carry out as the melting of the plastic fibre must be precisely controlled, otherwise the plastic fibre could be burnt, or damaged by a poorly aligned hot plate. Each of these methods is difficult to carry out in the field in that the surfaces of the fibre optic cables must be finished in a smooth manner and in a square manner relative to the length of the cable for abutment against a mating cable. As mentioned above, it is necessary for two abutting fibre optic cables to be as flush as possible to prevent an air gap between the two cables thereby presenting a difference in index of refraction between the two